The factors that initiate the conversion of proliferative population of post-embryonic skin epithelial cells into a non-proliferative population are being identified. Soluble and insoluble proteins at each stage of the maturation process are being isolated and characterized. Proteins from the cell surface from proliferative and non-proliferative populations of cells are being isolated and identified. Methods to isolate and maintain in cell culture ascinar cells from the sebaceous gland of the rabbit are being developed.